SWANSON, B.O.; Northern Arizona University: Terrestrial escape response of the mudskipper: an analysis of muscle power and kinematics

Recent research into steady swimming has greatly increased understanding of fish locomotion. However, studies of fish power production and performance during steady swimming are not considered maximal effort, and thus do not shed light on potential constraints on muscle performance. The fish escape response on the other hand is a fast, unsteady behavior, which should be under selective pressure for maximal performance. We avoided the assumptions inherent in complex hydrodynamic calculations of power by examining a terrestrial escape response in an amphibious fish. We examined jumping in Periophthalmus argentilineatus, a gobiid mudskipper. Seven individuals were coaxed to jump using a blunt probe. Jumps were recorded at 250 fps, either from a lateral or dorsal view using high-speed digital video. Movements of the center of mass and midline coordinates were analyzed. The kinematics of jumping, including inter-vertebral bending and timing variables, were quantified and compared to the escape responses of other fishes. Movements associated with the mudskipper jump included lateral and ventral bending. Mudskippers showed greater inter-vertebral bending than aquatic escape responses in other fishes. This bending could be required to place the caudal fin under the center of mass, or it could be a byproduct of the low viscosity of air compared to water. Models describing the kinetics of jumping were used to estimate the muscle power produced during the jump. Muscle mass specific power production during the jump was similar to the maximum values recorded for other poikilothermic vertebrates, and similar to what has been calculated for fish escape responses using hydrodynamic modeling.